Update:
The navigation has now been re-opened.
Presumably the contractors have deposited a layer of clay on the canal bed in the affected area. This swift re-opening is a happy contrast with a similar leak on the Huddersfield Narrow Canal which closed that canal recently for two weeks.

Today's leak near Parbold happened on a 27 mile long pound between Appley Bridge and Liverpool, so it could have become necessary to block off the canal on each side to prevent a major water loss had the repair not worked straight away.